Alpha-Particle-Driven Toroidal Alfven Eigenmodes In The Tokamak Fusion Test Reactor

Alpha-particle-driven toroidal Alfven eigenmodes (TAEs) have been observed for the first time in deuterium-tritium (D-T) plasmas on the tokamak fusion test reactor (TFTR). These modes are observed 100-200 ms following the end of neutral beam injection in plasmas with reduced central magnetic shear and elevated central safety factor [q(0) > 1]. Mode activity is localized to the central region of the discharge (r/a < 0.5) with magnetic fluctuation level <(B)over tilde (perpendicular to)> similar to 10(-5) and toroidal mode numbers in the range n = 2-4, consistent with theoretical calculations of alpha-TAE stability in TFTR.